She appeared to stumble onto the stage before hugging one of her guitarists. The singer seemed confused while adjusting her shoes, before taking one of them off and walking over to the microphone.

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The singer then mumbled and slurred through a performance of 'Just Friends'. The crowd reportedly booed throughout the concert as Winehouse continually left the stage, leaving her band playing on.

Local press outlets report that fans described the gig as a "scandal" and "disaster". Tickets for the concert were around Â£35 each.

One fan wrote on YouTube: "She started a show and turned her back to public (btw, for most of us it was not that easy to give the money for ticket because of the economic situation in Serbia) and that was just the beginning of her disrespect and bizarre behavior (sic).

"She did not sang one song from beginning to the end, Some of them she didn't even tried to sing. Not a fan anymore."

Winehouse is set to play at Istanbul's Kucuk Ciftlik Park in Turkey tomorrow night, with further dates in Greece, Spain, Switzerland, Italy, Poland, Hungary and Romania.

Her spokesman said: "Amy Winehouse has completed her assessment at the Priory Clinic in London and will continue as an outpatient.

"She is now looking forward to playing shows around Europe this summer and is raring to go. She would like to send a huge thanks to all her fans for the messages of support she has received over the last week and can't wait to see them."